A bearing, typically made of lubricious material, may be placed around a rotatable shaft to fit between a ledge or shoulder of that shaft and a surface which is not rotating or is rotating relative to the shaft. The shaft may, for example, be the stem of a valve and the non-rotating surface may be a ledge or shoulder of a valve housing in which the stem is rotating. Because of manufacturing variations, the axial dimensions of the stem and the housing may vary from valve to valve, as a result of which a particular valve may have either excessive stem wobble or excessive friction. There is a need for a bearing which will self-adjust for such axial variations and yet provide a bearing surface having the desired friction characteristics.
In other applications, a bearing, also typically made of a lubricious material, may be placed between a rotatable shaft and a sleeve in which the shaft rotates in order to reduce friction and facilitate rotation. For example, the shaft and the sleeve may be a stem and a housing of a valve. Because of manufacturing tolerances in the radial dimensions of the shaft and/or the sleeve, a given bearing may result in a loose fit in which the shaft may wobble or in a tight fit in which friction is greater than desired. There is, therefore, a need for a bearing which will self-adjust for radial variations and thereby minimize shaft wobble and yet provide satisfactory friction characteristics.
In still other applications, there may be a need for such a bearing which will self-adjust for both radial and axial variations and yet provide satisfactory friction characteristics.